Standards Organizations such as ISO and ANSI or system specifications specify image area positioning tolerances by denoting the maximum and minimum capture area on photographic film for a given format (i.e., size 135, size 126, size 120, size 110, APS, etc.). The minimum and maximum print area requirements for a photofinisher are also specified. These image area positioning tolerances allow the location of the exposed image to vary. This variability in image location leads to positioning difficulties when the film is scanned by a film scanner and subsequently re-scanned by the same or a different scanner. A key problem existing in current imaging systems is the difficulty in accurately repositioning of the image to the exact location of the previous scanning session.
Presently, photographic film is manually or automatically positioned in a film gate with the aid of perforation or edge detection schemes. Such perforation and edge detection schemes inherently have substantial position variability to their design when compared to digital image pixel resolution. This position variability can result in misaligned images if they are repositioned between multiple scans by the same or by different pieces of equipment. Many scanners mechanically move the film under a CCD array sensing head and convert the analog into a digital image. Due to mechanical registration tolerances, the film strip may be positioned under the sensing head differently each time. If the film is scanned in a different scanner, additional variabilities such as mechanical and resolution differences are introduced. For these reasons, a system to more accurately and repeatedly register the digital image for each scan is desired.